Monitoring for glass breakage over long periods of time by a wireless battery-powered detector requires that the detector be extremely power-efficient. Preferably, providing for such power efficiency includes, for example, ignoring irrelevant acoustic events which do not warrant triggering of an alarm. Additionally, a power-efficient detector is typically characterized by very low stand-by current consumption. However, a detector having a low stand-by current consumption is typically slow to respond to sudden and unexpected acoustic events.
Currently commercially available wireless glass breakage detectors include, for example, the ShatterPro™ sensor commercially available from UTC Fire & Security of Bradenton Fla. The ShatterPro™ sensor employs micropower electric microphones that do not include an embedded buffer. Due to inherent difficulties in matching the high output impedance of such microphones with currently available amplifiers, these detectors are ineffective in detecting low frequency sounds in the range of 10 Hz-50 Hz, which are the frequencies typically generated by glass breakage.
Other solutions have been proposed, such as those described in U.S. Pat. Nos. 5,192,931, 4,668,941, and 5,323,141. However, these solutions require relatively high power consumption, which renders them unsuitable for use with battery-powered detectors.